ThePigSite Pig Health

Encephalomyocarditis Virus (EMCV)

(206) The main reservoir host is the rat although mice may also spread it. It infects and causes disease in a wide range of vertebrate animals but pigs appear to be the most susceptible of farm animal species. The virus is world-wide but differs in pathogenicity and virulence in different countries and regions. One strain, type A, causes reproductive problems, a second strain, type B, causes heart failure and other strains are mild or non pathogenic. Both types A and B occur in Europe (e.g. Belgium) but in most countries of Europe, particularly those in the EU, it tends to be relatively mild or non-pathogenic and disease in pigs is rarely diagnosed.

In Australia the strains appear to be much more virulent for pigs than those in New Zealand. Virulent strains in Florida, the Caribbean and probably Central America damage the heart and cause death whereas those in the Mid West of the US tend to cause reproductive problems.

Clinical disease in pigs often occurs when rat numbers increase to plague levels. Pigs can be infected from rats or from rat-contaminated feed or water. It does not seem to spread very readily between pigs.

Clinical signsIn gilts and sows the first signs are often a few abortions near the end of pregnancy. Then over a period of about 3 months the numbers of mummified foetuses and stillbirths increase and pre-weaning mortality rises. The farrowing rate worsens. Affected females may go through a phase of fever and lack of appetite. In affected herds there are usually no clinical signs in weaned and growing pigs..

DiagnosisTo make a definitive diagnosis the virus has to be identified or rising antibodies demonstrated in blood samples taken two weeks apart.

Similar diseasesEMC could be confused with AD, PPV and PRRS although as you will see from Fig.6-2 there are distinguishing signs between these four. EMCV would be the last on the list of diagnostic priorities in Europe but to a lesser extent in the Mid West USA. Abortion or illness in sows or piglets due to PPV is uncommon and mummified pigs can be examined for the evidence of this infection.